1. Field of the Invention
The present invention relates to an in-vehicle power supply apparatus.
2. Background of the Invention
In-vehicle devices, which are electric loads installed in a vehicle such as an automobile, are generally supplied with electric power from a secondary battery, such as a lead-acid battery, or from an alternator. There are some in-vehicle devices, such as a steering motor, in which power consumption changes in accordance with, for example, a running condition of the vehicle. In such in-vehicle devices, a voltage of the secondary battery may fluctuate due to the running condition of the vehicle and an operation of the in-vehicle device may become unstable.
Accordingly, in the related art, for example, a technique is proposed in which an electric power, which is outputted from the secondary battery, is supplied to an in-vehicle device via a booster circuit device, and a target voltage of the boosting operation is adjusted in accordance with a state of the vehicle (see Japanese Laid-Open Patent Publication Nos. 2010-115010 and 2009-248748).
In the related art, there is a problem that, when a voltage of a secondary battery largely decreases and becomes lower than the lowest operating voltage of the booster circuit device, the boosting control becomes impossible and the voltage cannot be maintained within a normal range. In such a case, particularly, there is a problem that, an appropriate voltage is not supplied even for an in-vehicle device necessary for ensuring safety and thus making it difficult to ensure safety.
Accordingly, it is an object of the invention to provide an in-vehicle power supply apparatus that can supply an appropriate voltage to an in-vehicle device even in a case where there is a voltage fluctuation in the secondary battery.